Abstract

Background

Classical swine fever (CSF), caused by the Classical swine fever virus (CSFV), is an Office International des Epizooties (OIE) notifiable disease. However,
we are far from fully understand the distribution, tissue tropism, pathogenesis, replication
and excretion of CSFV in pigs. In this report, we investigated the dynamic distribution
and tissue tropism of the virus in internal organs of the experimentally infected
pigs using real-time RT-PCR and immunohistochemistry (IHC).

Results

A relative quantification real-time PCR was established and used to detect the virus
load in internal organs of the experimentally infected pigs. The study revealed that
the virus was detected in all 21 of the internal organs and blood collected from pigs
at day 1 to day 8 post infections, and had an increasing virus load from day 1 to
day 8 post infections. However, there was irregular distribution virus load in most
internal organs over the first 2 days post infection. Blood, lymphoid tissue, pancreas
and ileum usually contain the highest viral loads, while heart, duodenum and brain
show relatively low viral loads.

Conclusions

All the data suggest that CSFV had an increasing virus load from day 1 to day 8 post
infections in experimentally infected pigs detected by real-time RT-PCR, which was
in consistent with the result of the IHC staining. The data also show that CSFV was
likely to reproduce in blood, lymphoid tissue, pancreas and the ileum, while unlikely
to replicate in the heart, duodenum and brain. The results provide a foundation for
further clarification of the pathogenic mechanism of CSFV in internal organs, and
indicate that blood, lymphoid tissue, pancreas and ileum may be preferred sites of
acute infection.